The modulator has very little to do with the shift timing. It is in control of shift pressure (which is then used to make control pressure, so modulator pressure does eventually effect shift timing).

The delay for catalyst warming is made by applying vacuum to a bellcrank mechanism that changes the effect of the control pressure cable. You might locate and disconnect this vacuum and plug it. This would keep tha cat heating delay from happening and set a check engine light eventually. It will eliminate this possible defect though. I have never seen it happen but if the vacuum gets through to the control element it will change the shift profile.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician